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Watershed Boundary Dataset (WBD) Facts

History

  • 1974 - USGS / Water Resources Council mapped and published the 2-, 4-, 6-, and 8-digit drainages.
  • 1970's-80's - SCS (now the NRCS) mapped Watersheds and Subwatersheds. (Standards were few and dependent on local use or sponsor needs.)
  • 1992 - SCS National Instruction (NI 170-304) released for Hydrologic Unit mapping and digitizing. Provided a comprehensive set of instructions on delineating boundaries and digitizing.
  • 1996 - Comments received from USGS, FS and BLM on working draft. Many comments incorporated into standard, two delineation criteria differences exist.
  • 2000 - Federal Standards for Delineation of Hydrologic Unit Boundaries out for FGDC-Spatial Water Data Subcommittee member review and comment. Even though it is in draft format, states should be using it as the official guideline in 10 and 12-digit hydrologic unit delineation.
  • 2001 - December 6; The Spatial Water Data Subcommittee approved Version 1.0 of the Federal Standards for Delineation of Hydrologic Unit Boundaries.
  • 2004 - October 1; The Spatial Water Data Subcommittee approved Version 2.0 of the Federal Standards for Delineation of Hydrologic Unit Boundaries.
Watershed Definitions (as of March 19, 2018)
Name Level Digit Number of HUCs
Region 1 2 22
Subregion 2 4 223
Basin 3 6 387
Subbasin 4 8 2,318
Watershed 5 10 18,586
Subwatershed 6 12 101,534

Criteria

  • Scale at 1:24,000 and the base data meets or exceeds the USGS 7.5 Quad Sheets.
  • Delineation Basis
    • Hydrologically based
    • Crosses stream at confluence
    • May cross at other points if other HUs at same level are upstream
    • No delineations running down stream centerline

Interagency Standard

  • Interagency Standard for Delineation of Hydrologic Unit Boundaries
  • Sponsored by the Federal Geographic Data Committee (FGDC)
  • Subcommittee on Spatial Water Data with members from the:
    • Natural Resources Conservation Service
    • USGS
    • Forest Service
    • Bureau of Land Management
    • Corp of Engineers
    • Environmental Protection Agency
    • Federal Emergency Management Agency
    • National Oceanic and Atmospheric Administration
    • National Weather Service